1. Technical Field
The present invention relates to a semiconductor device.
2. Related Art
GaN-based semiconductor devices having one or more semiconductor layers mainly made of gallium nitride (GaN) have been known as one type of semiconductor devices (semiconductor elements). Some of the GaN-based semiconductor devices may serve as a MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor). In order to reduce the leak current on the interface of the semiconductor layer, relieve the potential crowding on the semiconductor layer and protect a junction surface between two semiconductor layers, a protective film is formed to coat the semiconductor layer in the GaN-based semiconductor device. The protective film is made of an electrical insulation material. In terms of reducing the potential damage of the semiconductor layer, wet etching is more preferable than dry etching for the etching process of the protective film.
JP 2008-198787A describes a protective film made of one type of electrical insulation material selected out of, for example, silicon dioxide (SiO2) and aluminum oxide (Al2O3). JP 2011-77123A describes separately forming two layers of a protective film made of silicon nitride (SiN), in order to form an opening structure below the working limit by photolithography. JP 2010-166040A describes forming a protective film made of, for example, silicon dioxide (SiO2) or silicon oxynitride (SiON) on a gate insulating film made of aluminum oxide (Al2O3), in order to suppress erosion of the gate insulating film during manufacture.